I have a problem that my plumber has been unable to fix on a couple of occasions. Very simply put, soon after I turn on the shower, a couple of minutes or so, I get a terrible rotten egg (sewer gas?) smell. I can't tell if it starts when it starts steaming up or just because. Shower is used daily. Sounds to me like a vent issue, but don't know where to start. Any suggestions?
SB